<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="timer"></div>
    <button id="timerId">取消延迟执行</button>
    
</body>
<script>
    /*
    在页面上生成动态时钟 2021-10-19 11:48:30
    setInterval()
    */
    function identify(num){
            return num < 10 ? "0" + num : num;
        }
    function creatTimer(){
        var date1 = new Date();

        var year = date1.getFullYear();
        var month = date1.getMonth() + 1;
        var day = date1.getDate();
        var hour = date1.getHours();
        var minute = date1.getMinutes();
        var sec = date1.getSeconds();    
    
        month = identify(month);
        day = identify(    day);
        hour = identify(hour);
        minute = identify(minute);
        sec = identify(sec);
        var result = year + "-" + month + "-" + day + " "+ hour + ":" + minute + ":"+ sec;
        return result;        
    }
    var timerId = setInterval(function(){
       var result = creatTimer();
       var timer = document.getElementById("timer" );
       timer.innerHTML = result;
    }, 1000)
    var btn = document.getElementById("btn");
    btn.onclick = function(){
        clearInterval(timerId);
    }
</script>
</html>